D.B.
I'm sure it's hormonal and will even off. I see that you've had some anxiety issues in the past, so those can kick off whenever you have a big change like this.
I wouldn't increase your dosage of Zoloft without talking with your doctor. You can't just monkey with milligrams and hope it works. And be sure you get a second pregnancy test before you do anything with meds at all. You never know. Besides, stopping nursing can mess with your cycles, so the 18 day window means nothing in terms of ovulation, so you have no idea where you are in your cycle anyway. That's throws off the pregnancy tests.
Your supplements are a bit odd - that piecemeal approach of a mineral for this and a mineral for that is very old school and ineffective. They used to say to "just take what you are low in" but that philosophy has been thrown out for a good 15 years although there are still a few doctors adhering to that model. But it's not advisable and there is little evidence that the body can use nutrients (vitamins, minerals, etc.) in isolation. Even standard multivitamin/mineral complexes have a lot more than that, and they are generally regarded as of minimal benefit. Same with those "Vitamin Water" flavors with 3 vitamins in this one, 2 in that one - just a marketing scheme with zero health benefits. So you not only are wasting money, you could be upsetting the balance in your body. I work in the field and we just never recommend this approach at all.
You could try adding exercise to help your mood. I know that may be hard if you are panicky and moody, nauseated and anxious.
Good luck - I hope you get this settled soon.